The invention relates to respiratory protection apparatuses comprising a breathing mask, a harness for fast donning, and sometimes goggles for protection against smoke, which may be integral with the mask or not.
Fast donning safety apparatuses for use by flight crew members of passenger planes are known which comprise a breathing mask with a regulator arranged for connection to a source of pressurized breathable gas (typically pressurized oxygen) and a harness having at least one extensible strap whose ends are connected to the mask and which has an element which is inflatable by the pressurized gas for extending a strap until it has a sufficient size for enabling the user to quickly don the harness over the head and deflatable to permit the strap to tighten, to urge the mask against the face and to maintain the mask on the face. The demand regulator is typically with air dilution. The mask may be designed for being fed with pressurized gas (which requires that the harness is able to exert a tension on the mask which is sufficient for air-tight contact of the mask with the face, in spite of the overpressure) or not.
Existing apparatuses of the above-defined type are hardly usable by crew members which wear a helmet and are located in a pressurized cabin designed for them to work, even at the maximum flight altitude of the plane, without a respiratory mask, although fast donning of the mask is required if depressurization occurs. That situation is that of crew members in military planes other than fighters (transport, patrol, reconnaissance, service, flight refueling planes for instance) which are often above a flight level which involves depressurization risks and/or which may be faced with invasion of smoke or toxic gas.
Overdimensizing an inflatable harness of an apparatus of the presently available type, to an extent sufficient for easy donning over a helmet, is not satisfactory. The force that a harness would have to exert for air tightness against the face (which is required under the most unfavorable depressurization conditions) would cause an unacceptable lack of comfort when such a situation is not present. The amount of tension exerted by an inflatable harness, except if so high that wearing the mask becomes unacceptable with a helmet during long periods, is not sufficient for retaining the mask on the face under exceptional conditions, such as in-flight ejection of crew members.